1. Field of the Invention
The present invention relates to a method and apparatus for evaluating the operating condition of a motor vehicle in which an output of an internal combustion engine is transmitted to a driving shaft via a torque converter of a change gear and a detection method thereof, and, more specifically, relates to an internal combustion engine misfire detecting device in such a motor vehicle in which an output of an internal combustion engine is transmitted to a driving shaft via a torque converter of a change gear. More the present invention specifically, relates to an internal combustion engine misfire detecting device in such a motor vehicle.
2. Description of Related Art
A conventional motor vehicle operating condition detecting method, for example an engine misfire detecting method, is disclosed in JP-A-4-209950(1992) in which through precise detection of engine rpm variation a misfire of a particular cylinder among a plurality of cylinders is detected based on an rpm increase after an ignition. In order to eliminate false readings based on rpm variation due to external causes such as bad roads other than engine misfire, such as information relating to respective wheel speeds and means for stopping misfire judgement based on signals from an accelerometer mounted on the vehicle body, are used.
However, it is necessary to mount rpm detection sensors at respective wheels for obtaining the wheel speed information and further it was difficult to correlate a wheel speed variation level with the engine rpm variation. Further, in the method wherein the misfire judgement is stopped when detecting vibrations with the accelerometer generated on the vehicle body due to bad roads, it is necessary to mount the accelerometer, and it was likely difficult to correlate an engine rpm variation starting point with an acceleration which required a substantial time for determining the control data therefor. Further, in case of a change gear using a torque converter there was a problem that it was difficult to accurately determine the time until a wheel load variation, such as a bad road, affects an engine load variation and the variation amount thereof.